Pipe jointing composition



Patented Dec. 8, 1953 2,662,019 PI'PE JOINTING COMPOSITION Raymond B.Seymour, Allentown, and Walter R. Pascoe, Reading, Pa., assignors to TheAtlas Mineral Products Company of Pennsylvania, Mertztown, Pa., acorporation of Pennsylvania No Drawing. Application March 14, 1951,Serial No. 215,630

1 Claim.

This invention relates to an improved sulfu pipe jointing compositionadapted for use in pipejoints of the poured type.

Molten sulfur alone and with admixtures has been used for some time forjointing various materials. These compositions have been used throughoutthe world under various proprietary names and have been successfullyused in this country for 50 years. One of the most successfulcompositions is that having a composition as follows: 58.8% sulfur, 38%graded silica aggregate of which 90% passes through a 325 mesh screen,2% carbon black and 1.2% Thiokol. This composition has been usedsuccessfully for years in jointing cast iron watermains. Thiscomposition greatly reduces initial leakage and has a great resistanceto vibration and thermal shock.

The sealing of this type of joint presumably depends upon a reactionbetween sulfur and iron in the presence of water, possibly to form ironsulfide. In properly constructed joints, a thin ring of black materialis observed at the ironsulfur interface and there is no noticeableprogression in the depth of this thin ring during years of service.However, if the joint is not properly poured or if there is settling ofthe ground, leaking of the joint will take place until sufficientactionbetween the sulfur and the iron has ensued to cause a rescaling of thejoint. This type of action is generally not detrimental to the life ofthe pipe but if there is continued settling of the ground or vibrationso that the resealing process must take place at frequent intervals,enough iron may be used up in the reaction to decrease the length ofservice of the pipe. Further, if corrosives such as sodium chloride arepresentin the water or in the sulfur compound, severe corrosion willtake place at the joint. 7

An object of this invention is to provide an improved sulfur compositionfor jointing pipes in which corrosion of the pipe at the interfacebetween the sulfur compound and the pipe is eliminated.

Another object of this invention is to provide an improved sulfurcomposition for jointing pipes in which the iron sulfide ring usuallyformed in this type of a joint is eliminated.

A laboratory method has been developed which gives a good insight intothe performance of sulfur jointing compositions in cast iron pipes. Inthese tests, a piece of cast iron such as a nail is inserted in a figureeight briquette filled with a sulfur jointing composition and the timefor corrosion to take place at the interface between the cast iron pieceand the sulfur composition when'the figure eight briquette is immersedin various solutions is measured. The figure eight briquette employed isidentical with that used in the A. S. T. M. standard method fordetermining tensile strength of hydraulic cement mortars. Thebriquette-gang mold is disclosed on pages 144-146 of the A. S. T. M.Standards 1949. When the briquette filled with sulfur jointingcomposition and having a cast iron piece inserted therein is immersed ina corrosive solution, there are generally two effects; either the castiron piece is completely corroded off at the interface or the sulfurcompound is split open at this point. It is believed that the latterphenomenon is the result of excessive corrosion. Using this method, itwas found that standard salt-free sulfur jointing compounds would last-200 days at a pH of 6-8 before the nail would be completely corrodedoff or before any cracking would take place. However, if 5% sodiumchloride is added to the sulfur compound, the time for cracking isreduced to 40 days. Since it is a well established fact that corrosionwith sulfur compounds is accelerated in the presence of sodium chloride,it was reasoned that if a material could be found to extend the time ofcomplete corrosion or cracking, that such a material would have asimilar effect in sulfur jointing compositiom. This is particularlyimportant since due to the shortages of lead, it is essential to usesulfur jointing compositions wherever possible and to ascertain thatsuch materials will outlast the cast iron pipe. In the series ofexperiments to be described, many compounds were tested but only a fewproved to be of interest using the criterion previously cited. Metallicpowders such as aluminum, lead, iron and zinc, as well as most of thesaits of these materials, did not decrease corrosion in any way. Forexample, the addition of 5% aluminum oleate allowed the material tocrack in a shorter time as 40 days. Similar effects were noted withaluminum phosphate, aluminum stearate and calcium stearate. Well knowninhibitors such as dibutyl thiourea and diethyl thiourea appeared tolengthen the time somewhat but these products decreased the strength ofthe sulfur compound to the point where it was not of practical value.Likewise, sodium benzoate which is also a well known corrosion inhibitorwas without effect, regardless of concentration. Sodium benzoateappeared to inhibit rust formation but greatly accelerated the formationof a black ring which is presumably iron sulfide,

Among the many other materials tried were various clays, triethanolamine, and phosphoric acid but none of these materials decreased thecorrosion. For example, the addition of as little as 3% Bentonite causedthe briquette to crack in tap water in 35 days. In this case, thecracking was very violent and caused the briquette to shatter. However,the addition of chromium compounds accomplished the object of thisinvention. Various chromium compounds may be employed, examples of whichare chromi'c oxide which may react with water to give chromic acid; zincchromate, lead chromate, barium chromate; sodium chromate and sodiumdichromate.

The utility of this invention cannot be ex plained completely since inactual pipe joints, it would take from 40 to 50 years to prove Successor failure. However, if the tests previously de: scribed aresignificant, it can be predicted that the life of sulfur joints has beenincreased by at least several hundred percent.

To prove that the corrosion resistant efiect obtained by the addition ofchromic acid or chromates to the sulfur compound was permanent and notdue to a leaching out of soluble chromates, the test using the figureeight briquette was conducted in running water. By analyzing the waterit was shown that no chromates were being extracted.

The quantity of chromic acid or chromates which may be added to thesulfur composition is variable and the range. of 0.5 to by weight of thesulfur composition is preferred.

The invention will be further illustrated by the following examples.

Example 1 A mixture of 58.8% sulfur, 38.8% graded silica aggregate, 2%carbon and 1.2% Thiokol was heated and poured in a figure eightbriquette. While this material was still molten, av cast iron piece wasinserted and allowed to be exposed above the surface. When this wasplaced in water at a pH of 6, the briquette cracked in 157 days. Whenthis was repeated at a pH. of 9, the briquette cracked. in days.

Example 2 Example 1 was repeated except that 2% sodium chloride wasadded to the sulfur composition. In this test the briquette cracked in4.6 days at a pH of 6.

Example 3 Example 1 was repeated except that 1% lead chromate was addedto the sulfur composition. In this test no cracking took place and thecast iron piece was not corroded off after 250 days;

Example 4 Example 1 was repeated except that 5% zinc chromate was addedto the sulfur composition.

In this test the briquette was unchanged after 300 days.

Example 5 Example 1 was repeated except that 3% chromic acid was addedto the sulfur composition. In this test no noticeable change had takenplace after 250 days. Similar effects were had with 1 and 5% chroniicacid.

Example 6 Example 1 was repeated except that 3% sodium chromate wasadded to the sulfur composition. In this test no change had taken placeafter 200 days in tap water even in the presence of sodium chloride.

Example 7 Asulfur composition similar to that employed Example 1 towhich 3% chromic acid was added was used to pour a pipe joint in theusual manner. .This joint was immediately put under pressure and thereWas a small amount of water lost during the first few hours but the pipejoint sealed completely within 2 days. There was no black iron sulfidering observable when the joint was out apart and inspected.

Example 8 To the sulfur composition employed in Example 1 was added 2%chromic acid and 1% lead chromate and a joint was poured in a 4" castiron watermain in the usual manner. This joint showed no leakage after 2days under a pressure of p. s. i. This joint was subjected to a 5 headof water for 18 months and showed no leakage. At this time, the jointwas cut apart and no pitting or any corrosion of any kind was noted atthe interface between the sulfur compound and the pipe. r v

It will be apparent to those skilled in the art that this invention issubject to wide application and the scope thereof is to be restrictedonly in accordance with the appended claim.

What is claimed is: j

A pipe jointing composition which consists essentially of a majorproportion of sulfur, a silica aggregate and a compound of chromiumselected from the group consisting of chromic acid, zinc chromate, leadchromate, barium chromate, sodium chroinate and sodium dichroniate, saidcompound of chromium being in the range of from about 0.5 to about 5% ofthe total weight of the sulfur and the aggregate.

RAYMOND B. saw/Lona. WALTER R. PASCOE.

References Cited in the file or this patent UNITED STATES PATENTS NumberName Date 1,749,541 Marr 1 Mar. 4, 1930 2,129,459 Benoit Sept. 6, 1938v2,280,301 Ray Apr. 21, 1942 2,331,270 George Oct. 5, 1943 2,416,295 EhleFeb. 25. 1947

